On weekday mornings, Mark Lynn, 10, walks past the 40-foot-tall metal fence looming over his backyard at the edge of his predominantly Catholic neighborhood in Belfast, and heads to his Catholic school, its crest displayed prominently on his blue sweater.

On the other side of the fence, children in the mostly Protestant Shankill neighborhood walk the opposite way toward their mostly Protestant schools.

In the 25 years since the Good Friday Agreement ended the bloody, sectarian conflict in Northern Ireland, the country has seen many changes — but not in its education system.

School attendance remains starkly divided along traditional religious lines. Even though the school system is state-funded and has one curriculum, Protestant church leaders dominate certain school boards while other schools are managed by the Catholic church. Students from either background are free to attend either type of school, but almost always choose the one matching their family’s religious tradition.

Lisa Lynn, 42, Mark’s mother, said she did not oppose integrated education. But she wants her son to attend Catholic school. “It’s not so much the religious side of it — I grew up a certain way,” she said, “and I want my kids to follow those footsteps.”

Despite a growing push for integrated education, less than 8 percent of Northern Ireland’s schools are formally integrated, where the religious background of the student body broadly reflects Northern Ireland’s demographics. While many schools have some children from both backgrounds enrolled, nearly one-third of schools have no religious mix at all.

The upshot: Many students do not meet pupils of different backgrounds until university.

That is a problem, said Darren McKinstry, the director of public policy at the Equality Commission for Northern Ireland, because shared learning plays an important role in re-establishing bonds after a conflict.

“This long experience of separate education has been a lost opportunity for everyone,” Mr. McKinstry said.

The divisions in Northern Ireland’s schools — most of which were established by the two churches — predate the 1921 founding of the state, when the island of Ireland was partitioned after centuries of British rule. The Republic of Ireland, which is majority Catholic, became self-governing while Northern Ireland, established in an area with the largest number of Protestants, remained part of the United Kingdom.

But Catholic nationalists wanted self-determination, and the result was the conflict known as the Troubles. Decades on, the two labels of Catholic and Protestant are clumsy shorthand for a deep-seated divide of cultural and political perspectives, even as the region grows increasingly secular and more diverse.

At Malvern Primary School, where most of the students come from a Protestant background, children gathered in the main hall for a spring assembly late last month. As they sang, thick Belfast brogues mingled with accents from Syria, Sudan and Afghanistan — from children whose families have found asylum in Northern Ireland.

These children of refugees are bused from across town, an arrangement that allowed the school to avoid closing after enrollment dwindled.

But there are no students from the nearby Catholic community.

“At this age, I would rather it stay the way it is,” said Lynsey McKinney, 40, whose daughter Jessica attends the school. “Maybe when Jessica is out working, then she will have to be in a mixed community. But at this stage, I just think it should be our own.”

At St. Joseph’s Primary School in the mostly Catholic Falls Road neighborhood nearby, a Virgin Mary statue greets students at the front door. The Pope’s photo hangs in the office. In a classroom, students practiced the Stations of the Cross, depicting Christ’s crucifixion, which they would perform at a local cathedral on Good Friday.

Dominic Fryers, a teacher, gave stage directions as children playing Roman soldiers mimicked nailing the child playing Jesus to a cross. There are children from other backgrounds enrolled here too — including a number of children born in Asia and Africa, Muslim students, and children with no religion affiliation. Some opt out of this religious education.

There are no Protestant children at the school.

Mr. Fryers, 34, who himself attended school here, said he encouraged his students to speak about politics, question authority, forge opinions and discuss the past.

“We spend half of the day teaching the children what to believe and then half of the day teaching them to question everything,” Mr. Fryers said with a smile.

The school’s history offers a reminder of the past. The previous school building was commandeered by the British military in 1971, and later, nationalist gunmen tried to stage an attack on police from the rooftop playground.

“It was a war zone, and lots of lives were lost around here,” said Jim McCann, the vice principal.

The old school was torn down and replaced by this new building. Its cage-like window grates were only recently removed. Now artwork adorns its hallways, and paper butterflies with the children’s future aspirations written on them hang from the ceiling. Some have written “police officer” — once unthinkable in a community where police were seen as the enemy.

We have come far, Mr. McCann, 67, said. “But there is still a way to go.”

His personal story is also a reminder of the country’s history.

A Belfast native, he became an IRA volunteer and was imprisoned in 1976 for 17 years for his involvement in an attack on a police officer. When he was released in 1994, he went on to get his teaching degree.

The school has partner programs with mostly Protestant schools to bring students together for projects, but some were financed by European Union initiatives that ended after Brexit.

In Glenarm, a small village tucked along the northeastern County Antrim coast, the community has long lived more intertwined and was spared the worst violence of the Troubles. Still, for a long time, children there remained largely divided in separate schools.

Then, in 2021, Glenarm’s Seaview Integrated Primary School became the first Catholic-maintained school to transform into an integrated school. The decision was as pragmatic as it was aspirational after enrollment dropped.

“I was looking out of my window, and I could also see two yellow buses leaving the village every day to take children to school elsewhere,” said Barry Corr, the principal. “And I knew that the school wasn’t providing for everyone, we had to do something.”

Parents and local community members voted in favor of the change.

“All the pictures of Mary had to go, the picture of the pope had to go,” Mr. Corr said.

The school is now 40 percent Catholic, 40 percent Protestant and 20 percent from other backgrounds, including different faiths and those with no faith.

Integration doesn’t mean there is no religion. In the morning, students say a prayer, which includes the line, “We are different and special together.” Teachers advise the children to pray the way they would at home.

Nicola Currell, 46, and a Protestant, said she was excited to send five of her children to the newly integrated school. They used to be bused six miles away, but now walk to Seaview.

“We very much were welcomed as a family,” she said. “There’s more of a variety of people from all kinds of backgrounds, and they love that.”

Back in Belfast, Hazelwood Integrated Primary School, Northern Ireland’s first integrated elementary school, has long stood as a model after parents came together across kitchen tables to push for change and founded the school in 1985.

“We try to create these little ambassadors, these little emissaries of peace,” said Jim McDaid, the principal. On one hallway wall, colorful paper fish are affixed to a board that reads: “We may all be different fish, but in this school, we swim together.”

“The furniture, the architecture of sectarianism, it’s normalized in our life,” he said, reflecting on the physical divisions in institutions like the schools, but also divisions over things like sports teams, pubs, newspapers, language and names.

The school sits in a sort of buffer zone between two communities — nestled against a 30-foot high fence visible from Mr. McDaid’s office that was built in 2008 after the mostly Catholic nationalist area was attacked by unionist neighbors.

“We talk about who built that with the students,” he said. “It wasn’t engineers that put that up, it’s entrenched attitudes. It’s intolerance that builds things like that. And I want kids to question that.”